oxidant + ze– → reductant
The electrode potential for a particular couple is a measure of the tendency of the reaction shown to proceed to the right.
The oxidant species and reductant species have an atom present in different oxidation numbers (Ce4+ and Ce3+), the oxidant being the species where the oxidation number is higher (Ce4+).
The standard potential for a redox couple (
E°) is a measure of tendency of the oxidant of the couple to accept electrons (the forward reaction above) when all substances are present in their standard state (unit activity).
The potential (
E) for couples having substances present in nonstandard concentrations or pressures can be calculated using the Nernst equation (
1).
RT/
F = 0.0257 V at 298 K
For
z = the number of electrons
Q is reaction quotient.